Perovskite quantum dots are emerging as attractive materials for photonic and optoelectronic applications. Patterning is an important step to incorporate them into display, anti‐counterfeiting, and ...optical chip applications. In this work, an in situ inkjet printing strategy is demonstrated for fabricating perovskite quantum dots patterns by printing perovskite precursor solutions onto a polymeric layer. Importantly, this strategy can achieve bright photoluminescence with a quantum yield up to 80% and shows broad applicability to a variety of perovskites and polymers. Moreover, the as‐fabricated perovskite quantum dots patterns are composed of a microdisks array on the surface of polymeric layer. The size of these microdisks can be varied by adjusting the printing temperature. To demonstrate the potential use in display and advanced anti‐counterfeiting applications, color pixel patterns and 2D code pattern are fabricated by varying the precursor solutions. The combination of superior photoluminescence properties, simple process, and low cost makes the in situ inkjet printing strategy very promising for patterning perovskite quantum dots toward photonic integrations.
An in situ inkjet printing strategy is developed for fabricating perovskite quantum dot patterns by printing perovskite precursor solutions onto a polymeric layer. The strategy is versatile, simple, and low cost to achieve color pixel patterns and/or 2D codes with strong photoluminescence, which are promising for anti‐counterfeiting and display applications.
Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but they suffer from low ...photoluminescence quantum yields at low excitation fluencies. Here we developed a ligand-assisted reprecipitation strategy to fabricate brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. To illustrate the photoluminescence enhancements in these quantum dots, we conducted comprehensive composition and surface characterizations and determined the time- and temperature-dependent photoluminescence spectra. Comparisons between small-sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2–8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br-rich surface. We further demonstrated wide-color gamut white-light-emitting diodes using green emissive CH3NH3PbBr3 quantum dots and red emissive K2SiF6:Mn4+ as color converters, providing enhanced color quality for display technology. Moreover, colloidal CH3NH3PbX3 quantum dots are expected to exhibit interesting nanoscale excitonic properties and also have other potential applications in lasers, electroluminescence devices, and optical sensors.
Perovskite quantum dots have been proven promising for photonic and optoelectronic applications, particularly, as bright and narrow band emitters for display technology. Despite the advantageous ...properties, the stability issues have to be resolved to unleash the full industrial potential of perovskite quantum dots in display technology.
In this paper, we reported the in situ fabrication of highly luminescent formamidinium lead bromide (FAPbBr3) nanocrystal thin films by dropping toluene as an anti-solvent during the spin-coating ...with a perovskite precursor solution using 3,3-diphenylpropylamine bromide (DPPA-Br) as a ligand. The resulting films are uniform and composed of 5–20 nm FAPbBr3 perovskite nanocrystals. By monitoring the solvent mixing of anti-solvent and precursor solution on the substrates, we illustrated the difference between the ligand-assisted reprecipitation (LARP) process and the nanocrystal-pinning (NCP) process. This understanding provides a guideline for film optimization, and the optimized films obtained through the in situ LARP process exhibit strong photoluminescence emission at 528 nm, with quantum yields up to 78% and an average photoluminescence lifetime of 12.7 ns. In addition, an exciton binding energy of 57.5 meV was derived from the temperature-dependent photoluminescence measurement. More importantly, we achieved highly efficient pure green perovskite based light-emitting diode (PeLEDs) devices with an average external quantum efficiency (EQE) of 7.3% (maximum EQE is 16.3%) and an average current efficiency (CE) of 29.5 cd A–1 (maximum CE is 66.3 cd A–1) by adapting a conventional device structure of ITO/PEDOT:PSS/TFB/perovskite film/TPBi/LiF/Al. It is expected that the in situ LARP process provides an effective methodology for the improvement of the performance of PeLEDs.
We report a facile nonaqueous emulsion synthesis of colloidal halide perovskite quantum dots by controlled addition of a demulsifier into an emulsion of precursors. The size of resulting CH3NH3PbBr3 ...quantum dots can be tuned from 2 to 8 nm by varying the amount of demulsifier. Moreover, this emulsion synthesis also allows the purification of these quantum dots by precipitation from the colloidal solution and obtains solid-state powder which can be redissolved for thin film coating and device fabrication. The photoluminescence quantum yields of the quantum dots is generally in the range of 80–92%, and can be well-preserved after purification (∼80%). Green light-emitting diodes fabricated comprising a spin-cast layer of the colloidal CH3NH3PbBr3 quantum dots exhibited maximum current efficiency of 4.5 cd/A, power efficiency of 3.5 lm/W, and external quantum efficiency of 1.1%. This provides an alternative route toward high efficient solution-processed perovskite-based light-emitting diodes. In addition, the emulsion synthesis is versatile and can be extended for the fabrication of inorganic halide perovskite colloidal CsPbBr3 nanocrystals.
The time evolution of the photoluminescence properties in phenylethylammonium tin halide perovskite (PEA2SnI4) film as a function of oxygen concentration is reported. Photo‐brightening and reversible ...photoluminescence quenching are observed in PEA2SnI4 film at ultralow oxygen concentration (< 1.5 vol%). In the case of 1.5 vol% < O2 < 21 vol%, the photoluminescence emission of PEA2SnI4 film can be partially recovered after resetting the samples to nitrogen box. As the oxygen concentration further increases with the range of 21 to 95 vol%, the photoluminescence emission of PEA2SnI4 film is significantly quenched and can only be slightly recovered after removing it to the nitrogen box. By correlating the material characterizations and theoretical analysis, the interactions between PEA2SnI4 and oxygen contain physisorption and chemical reactions are illustrated. Depending on the oxygen concentration, the chemical reactions between PEA2SnI4 and oxygen can be reversible and/or irreversible. The insights into oxygen concentration effects provide a guideline to optimize the stability of PEA2SnI4 for achieving high‐performance optoelectronic devices.
The temporal evolution of photoluminescence properties in phenylethylammonium tin halide perovskite (PEA2SnI4) film as a function of oxygen concentration is reported. The insights into the oxygen concentration effects provide a guideline to optimize the stability of PEA2SnI4 for achieving high‐performance optoelectronic devices.
In this work, the integration of in situ fabricated perovskite quantum dots embedded composite films (PQDCFs) as downshifting materials is first reported for enhancing the ultraviolet (UV) response ...of silicon (Si) photodetectors toward broadband and solar‐blind light detection. External quantum efficiency measurements show that the UV response of PQDCF coated Si photodiodes greatly improves from near 0% to at most of 50.6% ± 0.5% @ 290 nm. As compared to the calculated maximum value of 87%, the light coupling efficiency of the integrated device is determined to be 80%@395 nm, suggesting an efficient downshifting process. Furthermore, PQDCF is also successfully adapted for electron multiplying charge coupled device (EMCCD) based image sensor. The PQDCF coated EMCCD shows linear response with high‐resolution imaging under illumination at 360, 620, and 960 nm, implying the ability of broadband light detection in the UV, visible (VIS), and near infrared (NIR) region. Furthermore, a solar‐blind UV detection is demonstrated by integrating a solar‐blind UV filter with PQDCF coated EMCCD. In all, the use of PQDCF as luminescent downshifting materials provides an effective and low‐cost way to improve the UV response of Si photodetectors.
The in situ fabricated perovskite quantum dots embedded composite films (PQDCFs) are demonstrated to be excellent down shifting materials for enhancing the UV response of silicon photodetectors. In particular, PQDCF coated electron multiplying charge coupled device shows very good linear response with high resolution in the wavelength of UV–VIS–NIR region for broadband and solar‐blind light detection.
Perovskite quantum dots have been attractive building blocks for novel photonic devices development, where patterning is usually one of the most critical steps. We report on the combination of in ...situ fabrication and direct laser writing based on a 405 nm nanosecond laser, which provides an efficient and simple scheme for patterning perovskite quantum dots during the formation process. The as-fabricated gamma phase CsPbI3 quantum dots patterns show bright photoluminescence emission with a quantum yield up to 92%. By varying the key parameters of the direct laser writing, a minimum line width of 900 nm was achieved. A light-emitting optical grating with a period of 4 μm was fabricated and its polarization and structural color characteristics were discussed. The reported approach offers a route for fabricating patterned perovskite quantum dots with designed structures for photonic applications including micro-LED display, anticounterfeiting, and nanolasers.
Polarized light is very necessary to achieve functional optical systems for display, imaging, and information storage. Luminescent materials with polarized emission are of great interest to achieve ...polarized light. Here, strong polarized photoluminescence from stretched perovskite‐nanocrystal‐embedded polymer composite films is reported by combining an in situ fabrication process with controllable mechanical stretching. The material characterizations show that perovskite quantum dots (QDs) in stretched composite films are oriented aligned into wires along the stretching direction. The optical measurements illustrate that the stretched composite films exhibit not only isotropic absorption but also polarized photoluminescence emission. This feature can be explained with their unique structure of “QD‐aligned wires”. The achieved polarization ratio is consistent with the calculated results by considering the dielectric confinement of optical electric field and exciton–exciton interactions. In addition, the optimized stretched composite films show strong photoluminescence emission with a polarization ratio of up to 0.33 and a quantum yield of 80%. The use of these composite films in liquid crystal display backlights has potential to increase the light transmittance of polarizers from 50% (without considering the optical loss) to 65%, which is of great significance to improve the energy efficiency.
Perovskite nanocrystal‐embedded polymer composite films, which exhibit not only isotropic absorption but also strong polarized photoluminescence (PL) are fabricated by combining an in situ method and controllable mechanical stretching. The stretched composite films contain “quantum‐dot‐aligned wires” along the stretching direction in the polymeric matrix. The polarized PL can be explained by the dielectric confinement effect and exciton–exciton interactions.
